1. Field of the Invention
The present invention relates to an apparatus and a method for generating progressive polygon data, and an apparatus and a method for generating three-dimensional real-time graphics using the progressive polygon data.
2. Description of the Prior Art
In recent years, in the field of computer graphics (hereinafter, referred to as "CG"), a variety of circuit boards dedicated to three-dimensional (hereinafter, referred to as "3D") representation (hereinafter, simply referred to as "boards") and machines for rendering 3D graphics are commercially available. Among these, inexpensive boards are available to be built into a personal computer (hereinafter, referred to as "PC"), as Windows 95.RTM. and Windows NT.RTM. become widespread. Moreover, inexpensive game machines making use of such boards are also available.
Under these circumstances, most boards and game machines represent data for 3D graphics as polygons. Boards that handle polygons range from high-performance boards to low-performance boards. For example, in a high-performance board, a fine 3D object (hereinafter, referred to as "object") can be rendered with 10,000 polygons, whereas in a low-performance board, it is necessary to render an object with about 500 polygons.
Conventionally, when a creator of animation (hereinafter, referred to as "animator") produced real-time animation with an animation tool such as SoftImage.RTM. (product of Microsoft Co.), at least 30,000 polygons were generally required.
However, in order to render graphics in real time on a currently available PC, 2,000 is the maximum number of polygons for use in rendering. Moreover, when a plurality of objects are rendered simultaneously, it is necessary to restrict the total number of polygons for rendering all objets to about 2,000 polygons.
Japanese Laid-Open Patent Publication (Tokkai-Hei) No.7-85307 discloses a technique for the reduction of the polygon data used for rendering an individual object, when a plurality of objects are rendered. In this technique, a plurality of sets of polygon data that have different resolutions are prepared previously, and the resolutions are changed depending on what is rendered, e.g., what kind of behavior is rendered or the like.
This method makes it possible to reduce the number of polygons according to the behavior of an object or the like when rendering the object, so that this method is effective to display a plurality of objects on the screen.
When an animation is stored in the form of polygon data, a large storage area is generally required for storing one animation. The above-described technique requires a large amount of polygon data corresponding to a plurality of resolutions to be stored previously, so that a large storage area is necessary for storing the polygon data.
Furthermore, in the above-described technique, since the same polygon data cannot be used for machines with different performance, it is necessary to prepare as many sets of animation as performance levels of the machines. Therefore, not only a large storage area is necessary, but also a large amount of work is required from the animator.